This entry represents GRB2-associated-binding proteins 1-4 (Gab1-4) and similar proteins from animals. Proteins in this family contain one PH domain. GAB1 from humans and its orthologues dos and soc-1 from Drosophila and C. elegans [], respectively, function as adapter proteins that modulate intracellular signalling cascades triggered by activated receptor-type kinases. Gab1 from human plays a role in FGFR1 signalling, is involved in the MET/HGF-signalling pathway and functions as an important upstream regulator in EGF-mediated activation of mTORCs [, ].